Exercise Intensity and Longevity in Men-Reply

Abstract

<h3>In Reply.</h3> —Drs Pahor and Carbonin query our use of different classification criteria in analysis of physical activity and longevity in a cohort of Harvard alumni. We used three schemes for categorizing physical activity: (1) increments of 2100 kJ/wk; (2) quintiles of total energy expenditures (&lt;2524, 2524 to &lt;4738, 4738 to &lt;8001, 8001 to &lt;13142, and &gt;13142 kJ/wk), and (3) five categories each of vigorous and nonvigorous energy expenditure, using identical cutoffs (&lt;630, 630 to &lt;1680, 1680 to &lt;3150, 3150 to &lt;6300, and &gt;6300 kJ/wk). Since vigorous and nonvigorous energy expenditure add up to total energy expenditure, the cutoffs for category 3 are, of course, lower than those for category 2. Ideally, we would have used category 1 for all analyses; however, using increments of 2100 kJ/wk led to small numbers of deaths (&lt;50) within some categories (Table 2). Thus, for age-adjusted analysis, stable estimates for mortality rates could be